"Exception thrown and not caught" Error in batch.js file

While selecting the Dropdown values for Assignee field when creating an issue in Jira 5.0.7 an error was thrown with the below message. All the users of the respective project were not getting displayed in the dropdown list.

We have upgraded the Jira 4.4.4 version to Jira 5.0.7 a few hours back only.... Now we are facing this problem. Any help ???